BORED CAST-IN-PLACE STEPPED FOUNDATION AND ERECTION METHOD Russian patent published in 2006 - IPC E02D27/01 

FIELD: building, particularly to erect bored cast-in-place foundations of increased load-bearing abilities including ones having bottom marks typical to shallow foundations.

SUBSTANCE: stepped foundation comprises bored cast-in-place sections formed with the use of auger. Lower foundation step includes four peripheral cylinders of D_p.l. diameters and heights equal to above diameters. Peripheral cylinder centers are located at apexes of square having side lengths equal to D_p.l.. Square center coincides with center of support. Central support abutting four peripheral cylinders of lower foundation step has four expanded parts with D_c.exp diameters determined as D_c.exp=(1.0-1.2)D_p.l. and cylindrical bore having diameter D_p.up determined as D_p.up=(0.6-0.8)D_p.l.. Foundation bottom is 0.7 m below ground surface. Foundation erection method involves forming drilled pile sections; serially drilling wells having d_aug.1 diameters as each peripheral cylinder having D_p.l. is forming; creating each peripheral cylinder having height equal to D_p.l. by supplying working material for above cylinder forming; filling remainder well section with ground material, particularly with ground excavated from above object. Auger having diameter, which provides necessary D_p.l. diameter is used. The auger provides usage of technological processes, which provides 1.05-1.1 increase of pile diameter in comparison with auger diameter d_aug.1 and 1.1-1.2 increase of ground pile diameter in comparison with d_aug.1 diameter. After four peripheral cylinders of lower foundation step creation well having d_aug.2 diameter is drilled by means of direct auger rotation and ground excavation to day surface. The well has center coinciding with central support center and depth selected so that the well reach tops pf peripheral lower step cylinders. Then lower expanded part of central support is formed, wherein the expanded part has expansion degree B_c.exp./d_aug.2 equal to 1.5-2.0. During cylindrical bore drilling the expanded part has expansion degree D_p.up/d_aug.2 equal to 1.2-1.5.

EFFECT: increased load-bearing capacity per foundation volume unit, extended field of technical means.

3 cl, 4 dwg